After a volcanic super-eruption, humanity thrived
Supervolcanoes have the power to cough up enough ash to coat entire continents. They emit waves of hot gas, rocks and ash that flow down their slopes at speeds so great they strip away vegetation and kill anyone in their path. And they carve vast depressions in the planet, leaving permanent scars.
And yet, they might not be as apocalyptic as previously thought. About 74,000 years ago, a supervolcano at the site of present-day Lake Toba on the Indonesian island of Sumatra rocked our world. But while it was the largest volcanic eruption of the past two million years, a new study published in Nature suggests that humans not only survived the event – they thrived.
The study counters previous hypotheses, which suggest that the behemoth was so disastrous it caused the human species to teeter on the brink of extinction.
The Toba super-eruption expelled roughly 10,000 times more rock and ash than the 1980 Mount St Helens eruption. So much ejecta would have darkened skies worldwide, causing scientists to speculate that it might have plunged the Earth into a volcanic winter. In such a cold world, plants may have ceased growing, glaciers may have advanced, sea levels may have dropped and rainfall may have slowed.
Then in 1998, Stanley Ambrose, an anthropologist, linked the proposed disaster to genetic evidence that suggested a population bottleneck had occurred around the same time. He was certain that the Toba supereruption had caused the human population to decline to some 10,000 people.
The latest study, however, suggests that those theories are incorrect, says Michael Petraglia, an archaeologist at the Max Planck Institute for the Science of Human History who was not involved in the study. “We’re not seeing all the drama.”
More than 5,500 miles from the site of the Toba super-eruption in South-east Asia, Curtis Marean, an anthropologist at Arizona State University, and his colleagues discovered signs of its debris at two archaeological sites on South Africa’s southern coast.
Should Ambrose’s theory be correct, there would be fewer signs of human occupation in the layer of soil above the one with the signs of the Toba super-eruption. Marean’s team saw the opposite: after the catastrophic event, there were more signs of human occupation.
That doesn’t mean Toba’s volcanic winter never occurred. Marean speculates that an ensuing global chill
may have driven these prehistoric humans to the coast where they were able to survive.